Power converter including current sensor for providing information indicating a safe operation

ABSTRACT

An example of a power converter is disclosed. At least one converter module provides an alternating output voltage. The converter module is coupled to an output terminal by a conductor path. A current sensor is placed within a magnetic field generated by a current through the conductor path. The current sensor includes at least one magneto-resistive sensing element to provide a sensor signal in response to the magnetic field. A signal generator causes a magnetic self-test field at the magneto-resistive sensing element. A readout circuit receives a first sensor signal of the magneto-resistive sensing element before the magnetic self-test field is applied and a second sensor signal of the magneto-resistive sensing element after the magnetic self-test field is applied. An evaluation circuit determines information indicating a safe operation of the current sensor based on an evaluation of the first sensor signal and the second sensor signal.

TECHNICAL FIELD

Example embodiments relate to devices comprising magneto-resistivesensing elements for sensing of magnetic fields and concepts todetermine information indicating a safe operation of the device.

BACKGROUND

Devices comprising magneto-resistive sensing elements are used innumerous applications. For example, some current sensing devices usemagneto-resistive sensing elements in order to determine the magneticfield generated by a current through a conductor so as to be able toconclude on the size of the current based on the size of the magneticfield determined using the magneto-resistive sensing element.

Current sensors may, for example, be used to determine the currentflowing through or within a power module or power converter used toprovide an alternating supply voltage. Power converters of that kindare, for example, used to provide the supply voltages for electricmotors. Electric motors may be used for driving a vehicle or particularcomponent of the vehicle, for example a steering or the like.

In numerous applications, there is a desire to be able to determineinformation indicating a safe operation of the magneto-resistive sensingelement or the device containing it so as to be able to conclude whetherthe result determined using the magneto-resistive sensing element isreliable. Further, the information indicating a safe operation should bedetermined avoiding high additional costs or high consummation of spaceby additional devices.

SUMMARY

According to some example embodiments this may be achieved by a devicecomprising a signal generator to generate a signal causing a magneticself-test field for a magneto-resistive sensing element and a signalinput to receive a first sensor signal at a first time instant beforethe magnetic self-test field is applied and a second sensor signal at asecond time instant after the magnetic self-test field is applied. Anevaluation circuit of the device determines information indicating asafe operation based on an evaluation of the first sensor signal and thesecond sensor signal. Using a self-test field, information indicating asafe operation may be determined avoiding, for example, redundantmagneto-resistive sensing elements for the same purpose and theirassociated additional costs.

According to some example embodiments, it is determined that the deviceis in a safe operation state if a difference between the first sensorsignal and the second sensor signal corresponds to an expected sensorresponse to the magnetic self-test field. The difference of the firstsensor signals and the second sensor signal may be compared to theexpected response of the magneto-resistive sensing element to themagnetic self-test field.

Example embodiments of a current sensor comprise at least onemagneto-resistive sensing element to provide a sensor signal in responseto a magnetic field. A signal generator is configured to cause amagnetic self-test field at the magneto-resistive sensing element of thecurrent sensor. A readout circuit of the current sensor receives a firstsensor signal at a first time instant before the magnetic self-testfield is applied and a second sensor signal at a second time instantafter the magnetic self-test field is applied. An evaluation circuitdetermines information indicating a safe operation of the current sensorbased on an evaluation of the first sensor signal and the second sensorsignal which may serve to conclude whether the information on thecurrent as determined by the current sensor is reliable.

Example embodiments of a power converter comprise at least one convertermodule to provide an alternating output voltage, the converter modulebeing coupled to an output terminal by means of a conductor path. Acurrent sensor is placed within the magnetic field generated by acurrent through the conductor path. From the magnetic field generated bya single conductor path within the power converter, the current providedby the power converter may be determined within the power converteritself so as to be able to, for example, control electric motorsreceiving their supply voltage from the power converter. This may beachieved without additional external circuitry or components and withhigh accuracy so as to avoid additional costs, also in terms ofadditionally required space for further components next to the powerconverters.

BRIEF DESCRIPTION OF THE FIGURES

Some embodiments of apparatuses and/or methods will be described in thefollowing by way of example only, and with reference to the accompanyingfigures, in which

FIG. 1a schematically illustrates an example embodiment of a currentsensor;

FIG. 1b schematically illustrates an example embodiment of a currentsensor;

FIG. 2 schematically illustrates an example embodiment of a device;

FIG. 3 illustrates an example embodiment of a current sensor;

FIG. 4 illustrates an example of a magneto-resistive element to be usedwithin an example of a device or a current sensor;

FIG. 5 illustrates an example of a power converter for providing analternating output voltage; and FIG. 6 illustrates an example of a powerconverter for providing three phases of alternating current.

DETAILED DESCRIPTION

Various example embodiments will now be described more fully withreference to the accompanying drawings in which some example embodimentsare illustrated. In the figures, the thicknesses of lines, layers and/orregions may be exaggerated for clarity.

Accordingly, while further embodiments are capable of variousmodifications and alternative forms, some example embodiments thereofare shown by way of example in the figures and will herein be describedin detail. It should be understood, however, that there is no intent tolimit example embodiments to the particular forms disclosed, but on thecontrary, example embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of thedisclosure. Like numbers refer to like or similar elements throughoutthe description of the figures.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(e.g., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularexample embodiments only and is not intended to be limiting of furtherexample embodiments. As used herein, the singular forms “a,” “an” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. It will be further understood thatthe terms “comprises,” “comprising,” “includes” and/or “including,” whenused herein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, e.g., those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 illustrates an example embodiment of a current sensor 100,comprising at least one magneto-resistive sensing element 102. Themagneto-resistive sensing element 102 is used to generate or provide asensor signal in response to a magnetic field. The magneto-resistivesensing element 102 may, for example, be composed of or comprisematerial subject to the anisotropic magneto-resistive-effect (AMR),giant magneto-resistive effect (GMR), or colossalmagneto-resistive-effect (CMR). As illustrated in FIG. 1, it is assumedthat an external electromagnetic field 104 is to be measured by themagneto-resistive sensing element 102. The strength of the externalelectromagnetic field 104 causes a variance of the resistivity of themagneto-resistive sensing element 102. The variance of the resistivitymay be determined by means of a variance of a current flowing throughthe magneto-resistive sensing element 102 if a constant operatingvoltage is provided or by a change of a voltage over themagneto-resistive sensing element 102 if constant current is providedthrough the magneto-resistive sensing element 102. A signal generator106 of the current sensor 100 causes a magnetic self-test field 108 atthe magneto-resistive sensing element 102.

FIG. 1a illustrates one particular of numerous possible configurationsin which the self-test field 108 is directed opposite to the externalmagnetic field 104. According to further examples, however, the relativeorientation of the magnetic self-test field 108 and the externalmagnetic field 104 may be different. FIG. 1b illustrates furtherexamples in which the magnetic self test field 108 may be oriented inparallel or anti-parallel to a current direction 120 which is thedirection in which a current passes through the sensing element 102. Themagnetic self-test field 108 may also be applied without the presence ofan external magnetic field 104. A readout circuit 110 receives a firstsensor signal 110 a at a first time instant before the magneticself-test field 108 is applied and a second sensor signal 110 b at asecond time instant after the second sensor signal is applied. Accordingto some examples, one sensor signal of the first sensor signal 110 a andthe second sensor signal 110 b is determined while the magneticself-test field 108 is applied or superimposed, as illustrated in FIG.1a . According to further examples, the application of the magnetic selftest field 108 ends before the second time instant so that both thefirst sensor signal 110 a and the second sensor signal 110 b aredetermined without the simultaneous presence of the magnetic self testfield 108, as illustrated in FIG. 1b . An evaluation circuit 112determines information indicating a safe operation of the current sensor100 based on an evaluation of the first sensor signal 110 a and thesecond sensor signal 110 b. That is, information regarding thereliability or safe operation of the current sensor 100 is determined bythe evaluation circuit 112 in that a sensor signal is determined orreceived before and after the application of the magnetic self-testfield 108.

Using an embodiment may, for example, avoid the necessity to use shuntresistors and other current sensing devices. Determining current usingshunt resistors relies on the measurement of a voltage drop across asmall shunt resistor in order to calculate the output current. However,due to the shunt resistor, additional losses are generated and thereforethe overall effectiveness of the system is reduced. Furthermore, thelosses increase the temperature of the device and, due to thermalcoupling, the temperature of adjacent components which makes theirintegration in, for example, a power module a challenge. Embodimentsmay, for example, further avoid the use of other conventional currentsensors essentially being open loop transducers using hall-effectdevices, which have a high cost. Furthermore, the size of those currentsensors and their components makes their integration into devices to bemonitored almost impossible.

While some particular embodiments may read out or receive the secondsensor signal 110 b when no external field or the external magneticfield 104 is present, further embodiments may also apply a furthermagnetic self-test field at the second time instant provided that thefurther magnetic self-test field is different from the magneticself-test field at the first time instant.

According to some particular embodiments, the evaluation circuit 112determines that the current sensor is in a safe operation state if adifference between the first sensor signal 110 a and the second sensorsignal 110 b corresponds to an expected response of themagneto-resistive sensing element 102 to the magnetic self-test field108. A magnetic self-test field 108 of known characteristic or strengthmay be superimposed on the magneto-resistive sensing element 102 and thechange of the sensor signal as provided from the magneto-resistivesensing element 102 is compared to an expected change of a fullyoperational magneto-resistive sensing element having applied thereto anidentical magnetic self-test field 108. Once the expected sensorresponse is determined by an evaluation of the first sensor signal 110 aand the second sensor signal 110 b, it can be concluded that the currentsensor 100 is in a safe operation mode, that the readout and/or theresults obtained using the current sensor are reliable.

If the expected sensor response is not determined, a warning signal maybe generated. The warning signal indicates that the sensor signalsdetermined using the magnetoresistive sensing element are not reliable.This information may be forwarded to subsequent circuitry relying on thesensor signals by the warning signal. Depending on the particularimplementation, the warning signal may, for example, indicate one ofnumerous levels of reliability or integrity, for example according tothe IEC EN 61508 Standard (Functional safety ofelectrical/electronic/programmable electronic safety related systems).Further embodiments may use other standards based on IEC 61508 whichdefines four Safety Integrity Levels (SILs), with SIL 4 being the mostdependable and SIL 1 being the least. Automotive Safety Integrity Level(ASIL) is an example for functional safety definitions for applicationsin the automotive industry. For example, an electric motor may be drivenby a power converter which may necessitate the monitoring of the currentto the motor using a magneto-resistive sensing element. The current mayserve as an input to a closed loop control for operating the motor. Ifthe measurements from the magneto-resistive sensing element or the powerconverter comprising the magneto-resistive sensing element becomeunreliable, control loop circuitry or other circuitry may be informed bya warning signal compliant with ASIL. This may allow combiningcomponents of different manufacturers. In turn, the circuitry may decidethat a different mode of operation may be required in order to maintainsafe operation of the motor. Just as an example, it may be decided toswitch from closed loop control to open loop control disregarding theinformation on the measured current in the engine.

The magnetic self-test field 108 at the magneto-resistive sensingelement 102 may be generated using arbitrary technology. Some sensorreadout schemes, for example, employ a compensation coil to compensatethe external magnetic field 104 at the magneto-resistive sensing element102 if a current flows through the compensation coil. A correspondingreadout circuitry relies on balancing the current in the currentcompensation coil such that a superposition of a magnetic field asgenerated by the compensation coil to the external magnetic field 104leads to an effective field of zero seen by the magneto-resistivesensing element 102. This particular readout may compensate forlong-term drifts of the sensitivity of the magneto-resistive sensingelements and hence allow for a current sensor being stable and reliableover prolonged periods of use. According to some examples, thecompensation coil is further used to provide or generate the magneticself-test field 108 at the magneto-resistive sensing element 102. Tothis end, the signal generator 106 generates or causes a current throughthe compensation coil. This may allow to reuse already existingcircuitry in order to provide for the possibility to self-testing and toindicate whether the current sensor 100 is in a safe or reliable mode ofoperation or not.

Some examples use anisotropic magneto-resistive sensing elements(AMR-sensors). The AMR-sensing elements of some examples are operatedwith so-called AMR-flipping. A flipping coil is present within thecurrent sensor or within the sensor assembly which allows flipping of adirection of a magnetization of the anisotropic magneto-resistivesensing element. In particular, the flipping coil is configured togenerate a magnetic field parallel or antiparallel to the currentthrough the magneto-resistive sensing element which serves to inversethe sensitivity or response of the magneto-resistive sensing element.This may enable determination of offset values of the response of themagneto-resistive sensing element by using the mean-value of a firstsensor signal with a first magnetization direction and of a secondsensor signal with an opposite direction of magnetization, even at thepresence of external magnetic fields. By comparing two sensor signalswith opposite magnetization taken at the presence of an externalmagnetic field in subsequent time intervals, an intrinsic offset may bedetermined and compensated.

According to some embodiments, the flipping coil is used to provide themagnetic self-test field, i.e., the control signal generator generatesor causes a current through the flipping coil to enable thedetermination of the information indicating a safe operation of thecurrent sensor. According to some examples, the current used to generatethe magnetic self-test field in the flipping coil is smaller than aflipping current used to flip the magnetization of the anisotropicmagneto-resistive (AMR) sensing element.

According to further embodiments, no current is applied to the flippingcoils at the second time instant since a flipping current is appliedbetween the first time instant and the second time instant to flip adirection of the magnetization of an AMR sensing element, asschematically illustrated in FIG. 1b . The magnetic field generated bythe flipping current in the flipping coils causes a change of thedirection of a magnetization of the AMR sensing element 102 by roughly180 degrees and serves as the magnetic self test field 108. Thedirection of magnetization is either in parallel (130 a) oranti-parallel (130 b) to the direction 120 of a current through the AMRsensing element 102. Depending on the direction of the magnetization, asensor response or resistivity changes by a predetermined amount. FIG.1b illustrates the resistivity depending on the strength of an externalmagnetic field component 104 which is perpendicular to the direction 120of the current for both directions 130 a and 130 b of magnetization ofthe AMR sensing element 102. At a given external magnetic field 104, theresistivity of the AMR sensing element 102 jumps when the magnetizationis flipped. The jump is centered around an offset value given by themean value of the resistivity at the first time instant and theresistivity at the second time instant. If the offset value deviatessubstantially from an expected offset value or mean value, it may beconcluded that the magnetoresistive sensing element 102 is in anoperationally unsafe condition. The expected offset value may, forexample, be determined using a previous pair of measurement signals.According to those examples, the first sensor signal is determinedbefore the direction of magnetization of the AMR sensing element 102 isflipped and the second sensor signal is determined after the flipping.The change of the signal of the AMR sensing element is compared to anexpected response or change and if the expectation is not met,unreliable operation is suspected. For example, a first pair of a firstsensor signal and a second sensor signal may be used to determine anexpected offset value at a first measurement time and a second pair of afirst sensor signal and a second sensor signal may be used to determinea further offset value at a second measurement time. If the offset valuedeviates significantly from the expected offset value, it may beconcluded that the AMR sensing element 102 is in an unsafe or unreliableoperation state.

In some embodiments, the offset value determined by measurements withdifferent magnetizations may additionally be used to determine long termvariations of the sensing elements characteristics due to, for example,temperature changes or the like. That is, a variation of the offsetvalue as determined by two measurements with opposing magnetization maybe used to increase the accuracy of the sensor readout and to compensatefor long term effects while a strong variation of two subsequentlydetermined offset values may indicate an insecure or unsafe operationstate of the sensing element. According to some examples, the timeinterval between the first measurement time and the second measurementtime used to check the functional safety of the AMR sensing element maybe chosen shorter than a time interval in which long term variations ofthe AMR sensing element occur.

FIG. 2 illustrates an example of a device 200 comprising a signalgenerator 210 to generate a signal causing a magnetic self-test fieldfor a magneto-resistive sensing element. The device 200 furthercomprises a signal input 220 to receive a first sensor signal 220 a at afirst time instant before a self-test field is applied and a secondsensor signal 220 b at a second time instant after the self test fieldis applied. An evaluation circuit 230 determines information indicatinga safe operation based on an evaluation of the first sensor signal 220 aand the second sensor signal 220 b. A device 200 as illustratedschematically in FIG. 2 may be used to determine information indicatinga safe operation of an existing current sensor when the current sensoris operated or controlled by the device 200. The control signal 212 is,according to some examples, configured to cause a current through thecompensation coil of the magneto-resistive sensing element. According tofurther examples, the control signal 212 is configured to cause acurrent through a flipping coil of an anisotropic magneto-resistivesensing element to either cause a flipping of the magnetization of thesensing element or a superposition of an additional magnetic field bymeans of the flipping coils.

According to a particular embodiment, the evaluation circuit 230 isconfigured to determine that the magneto-resistive sensing element is ina safe operation state if a difference between the first sensor signal220 a and the second sensor signal 220 b corresponds to an expectedresponse of the magneto-resistive sensing element to the magneticself-test field.

FIG. 3 illustrates one particular example of a current sensor, havingfour AMR-sensing elements 302 a to 302 d coupled together as aWheatstone bridge. The Wheatstone bridge of the magneto-resistivesensing elements 302 a to 302 d are formed on top of an insulatingsubstrate 304, as for example a direct bonded copper substrate (DBC).

The substrate 304 is placed on top of a U-shaped conductor-path 306having the current to be measured by means of the current sensor 305 ofFIG. 3. The AMR-sensors or magneto-resistive sensing elements 302 a to302 d used in the embodiment of FIG. 3 are illustrated in detail in FIG.4 and are placed on top of the U-shaped conductor path 306 so that themagneto-resistive sensing elements 302 a and 302 b are on top of a firstsegment 306 a of the conductor path 306 and the magneto-resistivesensing elements 302 c and 302 d are on top of a second segment 306 b ofthe conductor path 306. The current through the individual segments 306a and 306 b flows in the opposite direction. Due to the geometricalposition of the magneto-resistive sensing elements, each pair ofmagneto-resistive sensing elements 302 a/302 b and 302 c/302 d mainlyexperiences the magnetic field provided by one of the conductor segments306 a and 306 b. The sensor signal as provided by the current sensor 306is generated using two compensation coils or compensation conductors 308a and 308 b placed on top of the magneto-resistive sensing elements 302a/302 b and 302 c/302 d so that a current generated through thecompensation coils generates a compensating magnetic field having itsfield vector 310 a, 310 b opposing to the field vector of a primarymagnetic field 312 a, 312 b generated by the conductor path 306. Areadout amplifier 314 is used to generate a current through thecompensation coils 308 a and 308 b so that an effective magnetic fieldbeing the superposition of the primary magnetic field 312 a/312 b andthe compensation magnetic field 310 a/310 b superimposes to a field ofzero at the position of the magneto-resistive sensing elements 302 a to302 d.

The current through the compensation coils 302 a and 302 b is a measurefor the magnetic field and, hence, a sensor signal being indicative ofthe current through the conductor path 306 is determined as a voltage atan output terminal 320 of the current sensor 305. By using a readoutwith compensation coils as illustrated in FIG. 3, a sensitivity driftmay be compensated for so that long-term stability can achieved.According to some examples, the compensation coils 308 a and 308 b arealso used to generate an additional magnetic self-test field for themagneto-resistive sensing elements so that their functionality may betested. For example, it may be indicated that the readout of the currentsensor 305 is reliable or that the magneto-resistive sensing elementsare functionally safe if a magnetic self-test field additionallysuperimposed by means of the compensation coils 308 a and 308 b causes aresponse of the sensor signal as it can be expected due to theadditional magnetic self-test field. In the example illustrated in FIG.3 this may be achieved by changing the control so that the primarymagnetic field 310 and the secondary magnetic field 312 do notcompensate completely but only to some predetermined amount. Theresultant current through the compensation coil can then be determinedas a sensor signal and evaluated if it corresponds to the expectedresponse or not to conclude on the functional safety of the currentsensor.

FIG. 4 illustrates in detail as to how an individual magneto-resistivesensing element may be composed. The following components of themagneto-resistive sensing element are formed on a common substrate. Theconductor path of the AMR-material 402 is running in serpentines and inparallel to a direction 404 which is parallel or antiparallel to thecurrent which is to be sensed. Compensation coils 405 run in parallel tothe direction 404 and on top of the AMR-material strips 402 on anopposite side to the conductor path 406. The AMR-strips 402 furthermorecomprise barber-pole shorting bars 408 which are, for example, becomposed of copper below the AMR-material or of gold above theAMR-material and which serve to generate a bi-polar response of theAMR-strips 402. The flipping coil 410 extends in a direction 412perpendicular to the direction 404 so that a current through theflipping coil 410 can be used to flip a magnetization of theAMR-material strips 402 to become parallel to the direction 404 oranti-parallel thereto. While one particular implementation of amagneto-resisting sensitive element is illustrated in FIG. 4, furtherexemplary embodiments may also use different configurations ormagneto-resistive sensing elements composed of different materials.

According to some of the embodiments discussed, a magnetic self-testfield can be superimposed or applied to the magneto-resistive sensingelements or AMR-strips 402 by either one of the compensation coil 406 orthe flipping coil 410 or by both of them simultaneously so as to allowto conclude whether the current sensor is operationally safe or reliableor not.

FIG. 5 illustrates a particular example of a converter module 500 ofpower module or power converter having at least one converter module 500to provide an alternating output voltage and an output terminal 502 ofthe converter module 500. An example of a current sensor 504 accordingto an embodiment is placed within the magnetic field generated by acurrent through a conductor path 507 coupling the converter module tothe output terminal 502. The converter module 500 comprises a firstinput for a negative supply voltage 506 a and a second input 506 b for apositive supply voltage. A first insulated gate bi-polar transistor 508a serves to couple the positive supply voltage 506 b to the outputterminal via the conductor path 507 and a second insulated gate bi-polartransistor 508 b serves to couple the negative supply voltage 506 a tothe output terminal 502 via the conductor path 507. Placing a singlecurrent sensor 504 within the magnetic field generated by the currentthrough the conductor path 507 allows measurement of the current throughthe power converter within the power converter itself so allowing forcompact and flexible devices. That is, the current drawn by, forexample, electric motors driven by a power converter 600 as illustratedin FIG. 6 can be directly measured within the power converter itself sothat the quantity used within the closed-loop control of the electricmotor can be determined with high accuracy and without the need ofadditional components next to the power converter, as it is requiredaccording to some conventional approaches.

FIG. 6 illustrates a further example of a power converter 600 consistingof three converter modules 602 a to 602 c as illustrated in FIG. 5 sothat an AC-voltage having three alternating phases can be provided. Thismay serve to drive an electric motor with the required supply voltages.

According to some exemplary embodiments, a current sensor as, forexample, illustrated in FIG. 3 is placed on top of the conductor path507 within a converter module 500 of a power converter 600. According tofurther embodiments, the conductor path 507 may exhibit a recess inwhich the current sensor is applied in a direction perpendicular to thesurface of the conductor path 507. This may serve to additionally savespace within the power converter 600, at the same time allowing toaccurately measure the current within the power converter 600 since thesensitive area of the current sensor is parallel to a magnetic fieldcomponent. In this particular example, the magnetic field component isgenerated by the edge of the recess within the conductor path.

In other words, FIG. 6 illustrates an inverter system usable forconverting high-voltage DC power into multi-phase AC power required todrive an electric. Most of the applications use a 3-phase inverterconsisting of three half-bridge legs, each of them connected to one ofthe three load terminals. A nearly constant DC-bus voltage (battery)supplies a full bridge consisting of six switches. By controlling theswitches, voltage pulse patterns are generated at the output terminals,which cause a sinusoidal current with an inductive load. The inverter isthus used to provide variable frequency output voltages and currents ofdifferent values. In order to provide the proper voltage and currentpatterns to the load (motor), the load current of the power module hasto be measured very precisely.

In summary, by integrating current sensors based on themagnetoresistance effect (MR) in the power module the cost and size ofthe whole system can be significantly reduced while not affecting theperformance of the inverter. The xMR (AMR-AnisotropicMagnetoResistance,GiantMagnetoResistance, TunnelMagnetoResistance) sensors allow apotential free measurement of the current via magnetic field. Thissensor measures the field in plane (field component which is parallel tothe plane of the current bar). The magnetic field of the primary currentin the power module will change the resistance of the MR sensor bridge.This resistor change generates an electrical output which may beprocessed electronically by an ASIC or μC. The MR sensors are made onsubstrates like—silicon, ceramics, polymers electrically isolated fromthe substrate and isolated from the primary current. Any bridgeconfiguration (half, full) as stand-alone sensor, monolithicallyintegrated with a evaluation chip or stacked chips may be used. A simplelinear output bridge may be used, also a gradiometric arrangement tosuppress stray fields or a matrix approach with TMR cells can be used. Amagnetoresistive sensor may be used, placed isolated in the vicinity (onthe top) of a shaped current bar in the DCB to measure the current inthe bar. The shape of the current bar may be designed to measure themagnetic field generated by the current just at one coordinate, at twocoordinates or more in the vicinity of the bar. The MR sensors maymeasure DC and AC currents from Milliampere to 1000 Ampere from DC to 5MHz. The sensor is not in electrical contact with the current bar(galvanic isolated) and with a modification on the sensor topology itcan be made functionally safe due to a self test principle (AMRflipping). FIG. 3 shows the closed loop compensation approach whichgives a high accuracy. FIG. 4 shows an AMR sensor with flipping andcompensation coils integrated on a chip. The sensor of FIG. 4 has nomagnetic core, avoiding saturation or hysteresis effects and allowingvery small devices which may enable its integration without using largeareas in the power module and so saving cost and increasing powerdensity. Due to the contactless magnetic measurement principle there isan inherent galvanic isolation between the high voltage IGBT parts andthe sensor output signal

The integration of current sensors into power modules may be desirablefor every power class starting from low power applications as forauxiliary drives or DC-DC converters up to high power applications asfor inverters or generators for full hybrids and electric vehicles. Theinternal layout of each half bridge may be adapted to make theintegration possible. A current rail (CR) may be designed into thelayout of the direct bonded copper (DBC) substrates for each halfbridge. At the top of the current rail a second small DBC may be fixedas carrier for the dual current sensors. The second ceramic helpssimultaneously to adapt the distance between current rail and sensor.The current rail (in which a current flows and the MR sensor detects themagnetic field in the vicinity) may be designed as a rectangular shape,with a slot inside or in a U-form.

Example embodiments may further provide a computer program having aprogram code for performing one of the above methods, when the computerprogram is executed on a computer or processor. A person of skill in theart would readily recognize that steps of various above-describedmethods may be performed by programmed computers. Herein, some exampleembodiments are also intended to cover program storage devices, e.g.,digital data storage media, which are machine or computer readable andencode machine-executable or computer-executable programs ofinstructions, wherein the instructions perform some or all of the actsof the above-described methods. The program storage devices may be,e.g., digital memories, magnetic storage media such as magnetic disksand magnetic tapes, hard drives, or optically readable digital datastorage media. Further example embodiments are also intended to covercomputers programmed to perform the acts of the above-described methodsor (field) programmable logic arrays ((F)PLAs) or (field) programmablegate arrays ((F)PGAs), programmed to perform the acts of theabove-described methods.

The description and drawings merely illustrate the principles of thedisclosure. It will thus be appreciated that those skilled in the artwill be able to devise various arrangements that, although notexplicitly described or shown herein, embody the principles of thedisclosure and are included within its spirit and scope. Furthermore,all examples recited herein are principally intended expressly to beonly for pedagogical purposes to aid the reader in understanding theprinciples of the disclosure and the concepts contributed by theinventor(s) to furthering the art, and are to be construed as beingwithout limitation to such specifically recited examples and conditions.Moreover, all statements herein reciting principles, aspects, andembodiments of the disclosure, as well as specific examples thereof, areintended to encompass equivalents thereof.

Functional blocks denoted as “means for . . . ” (performing a certainfunction) shall be understood as functional blocks comprising circuitrythat is configured to perform a certain function, respectively. Hence, a“means for s.th.” may as well be understood as a “means configured to orsuited for s.th.”. A means configured to perform a certain functiondoes, hence, not imply that such means necessarily is performing thefunction (at a given time instant).

Functions of various elements shown in the figures, including anyfunctional blocks labeled as “means”, “means for providing a sensorsignal”, “means for generating a transmit signal.”, etc., may beprovided through the use of dedicated hardware, such as “a signalprovider”, “a signal processing unit”, “a processor”, “a controller”,etc. as well as hardware capable of executing software in associationwith appropriate software. Moreover, any entity described herein as“means”, may correspond to or be implemented as “one or more modules”,“one or more devices”, “one or more units”, etc. When provided by aprocessor, the functions may be provided by a single dedicatedprocessor, by a single shared processor, or by a plurality of individualprocessors, some of which may be shared. Moreover, explicit use of theterm “processor” or “controller” should not be construed to referexclusively to hardware capable of executing software, and mayimplicitly include, without limitation, digital signal processor (DSP)hardware, network processor, application specific integrated circuit(ASIC), field programmable gate array (FPGA), read only memory (ROM) forstoring software, random access memory (RAM), and non-volatile storage.Other hardware, conventional and/or custom, may also be included.

It should be appreciated by those skilled in the art that any blockdiagrams herein represent conceptual views of illustrative circuitryembodying the principles of the disclosure. Similarly, it will beappreciated that any flow charts, flow diagrams, state transitiondiagrams, pseudo code, and the like represent various processes whichmay be substantially represented in computer readable medium and soexecuted by a computer or processor, whether or not such computer orprocessor is explicitly shown.

Furthermore, the following claims are hereby incorporated into thedetailed description, where each claim may stand on its own as aseparate example embodiment. While each claim may stand on its own as aseparate example embodiment, it is to be noted that—although a dependentclaim may refer in the claims to a specific combination with one or moreother claims—other example embodiments may also include a combination ofthe dependent claim with the subject matter of each other dependent orindependent claim. Such combinations are proposed herein unless it isstated that a specific combination is not intended. Furthermore, it isintended to include also features of a claim to any other independentclaim even if this claim is not directly made dependent to theindependent claim.

It is further to be noted that methods disclosed in the specification orin the claims may be implemented by a device having means for performingeach of the respective acts of these methods.

Further, it is to be understood that the disclosure of multiple acts orfunctions disclosed in the specification or claims may not be construedas to be within the specific order. Therefore, the disclosure ofmultiple acts or functions will not limit these to a particular orderunless such acts or functions are not interchangeable for technicalreasons. Furthermore, in some embodiments a single act may include ormay be broken into multiple sub acts. Such sub acts may be included andpart of the disclosure of this single act unless explicitly excluded.

What is claimed is:
 1. A power converting device, comprising: at leastone converter to provide an alternating output voltage through an outputterminal, the converter being coupled to the output terminal by means ofa conductor path; the at least one converter comprising; a currentsensor placed within a magnetic field generated by a current through theconductor path, the current sensor comprising at least onemagneto-resistive sensing element to provide a sensor signal in responseto the magnetic field; a signal generator to cause a magnetic self-testfield at the magneto-resistive sensing element; a readout circuit toreceive a first sensor signal of the magneto-resistive sensing elementat a first time instant before the magnetic self-test field is appliedand a second sensor signal of the magneto-resistive sensing element at asecond time instant after the magnetic self-test field is applied; andan evaluation circuit to determine information indicating a safeoperation of the current sensor based on an evaluation of the firstsensor signal and the second sensor signal.
 2. The power converter ofclaim 1, further comprising: a first Insulated Gate Bipolar Transistorto couple a positive supply voltage to the output terminal via theconductor path; and a second Insulated Gate Bipolar Transistor to couplea negative supply voltage to the output terminal via the conductor path.3. The power converter of claim 1, comprising three converters togenerate an AC current having three alternating phases.
 4. The powerconverter of claim 1, further comprising: at least one compensation coilto compensate an external magnetic field at the magneto-resistivesensing element at least partly if a current flows through thecompensation coil, wherein the signal generator is configured to cause acurrent through the compensation coil.
 5. The power converter of claim1, comprising four magneto-resistive sensing elements, themagneto-resistive sensing elements being coupled as a Wheatstone bridge.6. The power converter of claim 1, wherein the magneto-resistive sensingelement is an anisotropic magneto-resistive sensing element.
 7. Thepower converter of claim 6, further comprising: at least one flippingcoil to flip a direction of a magnetization of the anisotropicmagneto-resistive sensing element.
 8. The power converter of claim 7,wherein the signal generator is configured to cause a flipping currentthrough the flipping coil, wherein the flipping current is a currentused to generate a magnetic flipping field used to flip themagnetization of the anisotropic magneto-resistive sensing element. 9.The power converter of claim 8, wherein the signal generator generates asmaller current through the flipping coil than the flipping current. 10.The power converter of claim 1, wherein the evaluation circuit isconfigured to determine that the magneto-resistive sensing element is ina safe operation state if a difference between the first sensor signaland the second sensor signal corresponds to an expected offset of themagneto-resistive sensing element.
 11. The power converter of claim 1,wherein the evaluation circuit is configured to determine that themagneto-resistive sensing element is in a safe operation state if adifference between the first sensor signal and the second sensor signalcorresponds to an expected response of the magneto-resistive sensingelement to the magnetic self-test field.
 12. The power converter ofclaim 1, wherein the signal generator is further configured to cause afurther magnetic self-test field after the second time instant.